Multiple function, self-repairing composites with special adhesives

ABSTRACT

A system for self-repairing matrices such as concrete or cementitous matrices, polymeric matrices, and/or fibrous matrices, including laminates thereof. The system includes repair agents retained in and/or on vessels, such as hollow fibers, within the matrix. Upon impact, the vessel rupture, releasing the chemicals. For multi-layer laminates, the systems provides a total dynamic energetic circulation system that functions as an in situ fluidic system in at least one layer or area. The energy from the impact ruptures the vessels to release the chemical(s), and mixes the chemical(s) and pushes the chemical(s) and/or resulting compound through the matrix. The repair agents can withstand high temperatures, such as the heat of processing of many laminates, e.g., 250-350° F.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuing application of U.S. Ser. No.11/428,132, filed on Jun. 30, 2006, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/695,548, filed Jul. 1, 2005,entitled Systems for Self Repair & Adhesives for Self Repair ofComposites, all of which are incorporated herein by reference in theirentirety.

BACKGROUND

The present invention generally relates to matrix materials for use in awide variety of end use fields and applications. More particularly, theinvention relates to self-repairing, settable or curable matrix materialsystems, containing reactive chemicals used in conjunction with releasevessels or conduits such as fibers, the functions of which may bemultiple.

Composites include at least two materials: the matrix and inclusions,such as reinforcement fibers or particles. Failures often occur at theinterfaces between the matrix and fibers or particles. To preventfailure and fatigue, good bonding between the materials is needed.Numerous systems and techniques for repairing failed composites havebeen proposed.

Dry, a former professor at the University of Illinois, in severalpatents the invention for which she conceived and developedindependently by 1990, e.g., U.S. Pat. Nos. 6,261,360, 5,989,334,5,660,624, 5,575,841, and 5,561,173, described a cured matrix having aplurality of hollow release vessels, usually fibers, dispersed therein,the hollow fibers having a selectively releasable modifying agentcontained therein, means for maintaining the modifying agent within thefibers until selectively released, and means for permitting selectiverelease of the modifying agent from the hollow fibers into the matrixmaterial in response to at least one predetermined external stimulus.The cured matrix materials have within them smart fibers capable ofdelivering repair agents into the matrix wherever and whenever they areneeded.

In Dry's patents discussed above, damage was repaired by fiberscontaining modifying agent. Dry found that fibers, for retaining thechemical modifying agent, were easier to break than beads, they couldcover damage which occurred over a larger area, could preserve strengthof the structure, could act as a reservoir to retain larger volumes ofagent therein than beads and, if the ends protruded, more chemical couldbe added.

Another researcher group, Professors Sottos, White and Moore at theUniversity of Illinois, has made various attempts to provideself-healing composites starting in 1993, nearly 4 years after Dry'sinitial work. One design was to use a fairly expensive active chemical,such as dicyclopentadiene (DCPD) or Grubbs ruthenium in the matrix withdicyclopentadiene (DCPD) in beads. See, for example, U.S. Pat. No.6,518,330. This approach, using very small beads and such a livingchemical system, was designed to not require much force of damage butinstead relied on small forces and predict a an automatic full reactionto pull the chemical out of the bead beads once the reaction hasstarted. An article in Nature magazine by White, S., Sottos, N., et al.,Autonomic Healing Polymer Composites, Feb. 15, 2001 describes this.However, the research group later discovered that the Grubbs rutheniumruins the polymer matrix as described in. Their solution was toencapsulate the ruthenium; see U.S. Patent Publication No. 2005/0250878A1, entitled “Wax particles for protection of activators, andmultifunctional autonomically healing composite materials”. Theirsolution was to encapsulate the Grubbs ruthenium in wax in the matrix.

Subsequently, an elaborate system, called microfluidics, was developedby this group at the University of Illinois that included formingmultiple layers of tubes, from a solidified ink which is then coated andthe ink removed based on an ink developed at Sandia labs. The systemincludes in the matrix, a pump, valves in tubes to control chemicalflow, and mixing towers to provide among other capabilities, compositeswith self-repair properties. See, for example, U.S. Patent PublicationNo. 2004/0226620 “Microcapillary networks”. See also, for example, FIG.10, which schematically illustrates the self-repairing system withmicrofluidic aspects developed by University of Illinois. It requires aseparate form piece for all the functions such as mixing towers,delivery tubes in all or most layers, a pump and valves to start andstop the flow in the tubes. The valves could be operated based on pH,and suggestions by others have been made to use light to modulate thevalves.

U.S. Pat. No. 5,803,963 to Dry describes a self forming composite withan ongoing chemical reaction in which one chemical is released from afiber into a mold containing two powders and that chemical reacts withone powder in the mold and in that reaction, a product is produced whichreacts with the other powder in the mold. A polymer ceramic can be madein this way or other self forming composites.

U.S. Pat. No. 6,750,272, described a method for making afiber-reinforced composite, the method including dispensing a reactiveliquid into a mold, with the mold including fibers and asingle-component activator on the fibers.

U.S. Patent Publication No. 2004/0007784 to Skipor et al., who workedwith the White group at University of Illinois, describes a self-healingpolymer composition containing a polymer media and a plurality ofmicrocapsules or beads of flowable polymerizable material dispersed inthe polymer media, where the microcapsules of flowable polymerizablematerial contain a flowable polymerizable material and have an outersurface upon which at least one polymerization agent is attached. Themicrocapsules supposedly are effective for rupturing with a failure ofthe polymeric media, and the flowable polymerizable material reacts withthe polymerization agent when the polymerizable material makes contactwith the polymerization agent upon rupture of the microcapsules. This isdescribed as a way of making an initial cured form.

U.S. Pat. No. 6,858,660 to Scheifers et al. described a self-joiningpolymer composition, comprising a polymer, a plurality of amine pendantgroups attached to the polymer and a plurality of microcapsules offlowable polymerizable material dispersed in the polymer where themicrocapsules of flowable polymerizable material including microcapsulesand flowable polymerizable material inside the microcapsules. Themicrocapsules are effective for rupturing with a failure of the polymerso the flowable polymerizable material cross-links with the reactablependant groups upon rupture of the microcapsules.

Different techniques for formation of a composite structure arediscussed in U.S. Patent Publication No. 2003/0119398 to Bogdanovich etal., where a resin distribution system and method for use in resintransfer molding includes using a 3-D orthogonal fiber structure havingsmall channels therein for permitting a fluid to flow through thestructure for formation of cured composites for use in such processes asresin transfer molding. The 3-D orthogonal fiber structure includes awoven system, having X-, Y-, and Z-direction fiber, each of havingsubstantially no crimp within a body of the structure, thereby providinga system for distributing the fluid uniformly through the structure.

Other attempts have been made to provide self-repairing composites byother groups which used release from hollow fibers. See, for example,Motuku et al., from the University of Alabama, in “Parametric Studies onSelf-Repairing Approaches for Resin Infused Composites Subjected to LowVelocity Impact”, Smart Material Structure 8 (1999) 623-638, studied lowvelocity impact response of glass fiber reinforced composites, whichsupposedly had the potential to self-repair both micro- andmacro-damage. This University of Alabama group researched low velocityimpacts for self-repair in fiberglass composites which were prepared ata fairly low temperature, sufficient to make fiberglass samples. Theirstudies focused on a two part system which needed, in general, mixing ofmore than one minute.

In the U.K., Bristol University researchers Ian Bond and Richard Traskused psuedoimpact and then heat to release and heat to cure self-repairagents in glass tube mats placed on or in composites, the technologysuitable for use in a space environment. Still other tactics aredescribed, for example, in “Bleeding Composites'—Damage Detection andSelf-Repair using a Biomimetic Approach”, Pang et al., Composites: PartA 36 (2005) 183-1888.

Various matrix materials without separate chemical release inclusions,which are said to have self repairing properties, have been developed bynumerous researchers; for example, studies have been ongoing byProfessor Wutl of UCLA, at VPI and SU (Virginia Polytechnic Instituteand State University), and at NASA Langely. Some of these developedsystems are designed to reversibly repair damaged composites, but thematerials are generally not strong enough for structural applications.One shortcoming is that many of the systems need heat to trigger theself-repair chemistry. Prof Wutl suggests applications such as the glassin car headlights or heated windshields, where a heat source is readilyavailable, for use of the self-repair system. The NASA system is usedfor ballistic damage where heat may be produced.

The subject of self-repairing composite materials not only includesconcretes and polymeric materials, in addition to headlights andwindshields, it has been suggested that housings and other parts of cellphones, computers and perhaps batteries could be made self-repairing.See, e.g., U.S. Patent Publication No. 2005/0027078 to Scheifers et al.,which used chemistry to repair low energy damage such as in computercasings or cell phones by use of reactions which are self perpetuating.Other suggested self-repairing products include golf balls and tires.

The ideas for self-repairing composites are now widespread, butprocessing of the products under heat, development of adequate repairchemicals in terms of heat resistance, speed of repair, and simplesystems which use an in-situ system of energy and chemical flow in acirculation system to repair well, systems to repair medium to highimpact damage, multi-use applications, and applications to new end usesare all areas needing solutions and invention.

SUMMARY

The present invention provides alternate designs and/or solutions tomost of the drawbacks encountered in the prior art. The disclosureprovides processing of the products under heat, development of adequaterepair chemicals in terms of heat resistance, speed of repair, andsimple in-situ systems which use the an in situ system of energy andchemical flow in a circulation system to repair well, systems to repairmedium to high impact damage, fatigue damage, as well as selfforming/self repairing composites as well as other multiple functionalor multi-use applications. In the simplest form, in order to beself-repairing, a special, and applications to new end uses are allareas needing solutions and invention.

The present disclosure provides various elements, such as different andbetter repair conduits, alternate constructions for the repair conduits,alternate manners of having the repair conduits (e.g., fibers orchannels), different and better modifying agent is stored in a conduitembedded in a matrix. When the resulting composite is damaged, thedamage progresses through the composite matrix, breaking the conduit andreleasing the modifying agent. The modifying agent flows into the crackand re-bonds the cracked or delaminated faces.

An opportunistic dynamic notion of materials is included in thisapproach of self-repairing materials, in that it can go beyondself-repair, from changing and problem solving into new totally dynamicstructures in terms of their energy, design for material flow, andchemical change of the materials. The self-repairing composites of thisdisclosure utilize a system of liquid flows, energy applications andresponse, and chemical reactions, all in a synchronized way. The energyin the circulation system may come from any of the aspects involved suchas the force or damage, the repair conduit, a coating on the repairconduit, the modifying agent (which can be present in several partsand/or in several locations of the system), inclusions in the matrixsuch as beads or particles, the matrix itself, and the interactions ofvarious factors such as flow, energy produced by flow, damage andmaterial properties.

The present disclosure is to a composite matrix, including polymercomposite laminates, having a plurality of hollow repair conduitsdispersed therein, a modifying agent present within the repair conduitsand/or thereon, and means for permitting selective release of themodifying agent from the repair conduits into the matrix material inresponse to at least one external stimulus. Two examples of repairconduits are hollow repair fibers and channels. In most embodiments,reinforcing fibers are also present throughout the matrix. The matrixand the repair conduits together form an in situ fluidic system thattransports the modifying agent(s) throughout the matrix.

In many embodiments, the matrix, including the modifying agent andrepair fibers, is particularly suited for use in or processing underhigh temperature applications, e.g., at least 250° F., often 250-350°F., for extended periods of time, such as 1-3 hours. In many of theseembodiments, the modifying agent is sufficiently heat stable towithstand the high temperatures. In embodiments where the stability ofthe modifying agent under high temperatures is questionable, themodifying agent can be put into the fiber after the high temperatureprocessing. In most embodiments, the resulting article can withstandheat of use of the article and can also withstand any heat generated inthe article during use.

Additionally or alternatively, the cured matrix is particularly suitedto be a layer in a laminate material, e.g., a material having at leastone self-repairing layer. The cured matrix is particularly suited foruse with graphite and fiberglass laminates, which typically have to beprocessed at high temperatures.

The modifying agent may be present within the repair conduits (e.g.,within the hollow repair filter) on a surface of fibers, or both.Additionally, other modifying agents, either the same or different thanthe first modifying agent, may be present at locations other than therepair conduits, for example, distributed throughout the matrix. In someembodiments, the modifying agent(s) may be encapsulated or beaded.

The repair conduits may be present as randomly dispersed conduitsthrough the matrix or may be positioned in an orderly manner as in alayer of a laminate. In some embodiments, the ends of the repairconduits are engulfed or otherwise retained in the matrix, or the endsmay extend out to the edges of the matrix for later refilling if needed.Generally, the ends of the repair conduits are sealed in the finalcomposite, to retain the modifying agent therein. For embodiments wherethe repair conduits are fibers, the ends are typically sealed withadhesives, heat or other manner.

In some embodiments, especially those where the resulting composite is alayer in a laminate, the reinforcing fibers, if present, can be providedas an orderly network of fibers. The reinforcing fibers could be presentas a dense woven or knitted mat, or be present as a lofty non-woven mat.In other embodiments, whether in a laminate or not, the reinforcingfibers could be randomly dispersed throughout the matrix.

The present disclosure, in its most basic form, is directed toself-repairing systems that retain a modifying agent until needed. Thesystems include a matrix having a plurality of hollow repair conduitsdispersed therein, a modifying agent present, at least, within therepair conduits and/or thereon. Upon a predetermined stimulus, themodifying agent is released from the repair conduits into the matrixmaterial. The matrix and the repair conduits together form an in situfluidic system that transports the modifying agent(s) throughout thematrix. In many embodiments, the matrix, including the modifying agentand repair conduit, is particularly suited for use in or processingunder high temperature applications, e.g., at least 250° F., often250-350° F., for extended periods of time, such as 1-3 hours.

One particular aspect of this disclosure is a self-repair system havinga modifying agent present in a conduit. The modifying agent can be aone-part system or a two-part system; for a two-part system, typicallyonly one part is retained in the conduit, or, the second part isretained in a second conduit. The conduit is configured to retain themodifying agent until appropriate external stimulus, at which time themodifying agent is released. The modifying agent is configured to reactand repair any damage within the matrix. At least the modifying agentcan withstand without degradation exposure to high temperatures, e.g.,at least 250° F., often 250-350° F., for extended periods of time, suchas 1-3 hours.

Another particular aspect of this disclosure is a self-forming system inwhich conduits form a weave or 3-D structure. At least one part of themodifying agent is within the conduits, and a second part, for atwo-part modifying agent, can be in or on the fiber weave or structure.Upon appropriate stimulus, the conduit releases the internally heldmodifying agent, which contact and react with the second part,optionally forming the matrix. This system can make composites,laminates, or pre-pregs which can be activated later. In someembodiments, the modifying agent can withstand without degradationexposure to high temperatures, e.g., at least 250° F., e.g., at least350° F. for 1-3 hours.

An aspect of this disclosure is to provide a polymer graphite compositelaminate, preferably having 24-32 single plies, in which the laminate isself-repairing, by inclusion of repair conduits with repairing modifyingagent. The repair modifying agent can resist temperatures of at least250° F. for at least one hour and in some embodiments even at least 300°F. for 2 hours, in the usual oven ramp for carbon pre-preg. Even atthese temperatures for these times, the repair modifying agent remainssufficiently strong to repair the laminate after impact of 5 to 50joules to about 70-80% of the non impacted control. This laminate may bea graphite laminate. The repair conduits may be glass tubes. Therepairing agent could be an epoxy, including an epoxy vinyl ester, avinyl ester or an acrylate, such as a cyanoacrylate. In someembodiments, the repairing agent can be modified to provide desiredproperties such as heat resistance, fast chemical reaction, strength,later water proofing and longer shelf life.

Another aspect of this disclosure is to provide a polymer compositelaminate, e.g., having 24-32 single plies, in which the laminate isself-repairing. The laminate has conduits, such as tubes or channels,with repair modifying agent(s). The repair agent can resist heat of atleast 250° F. for at least one hour and, in some embodiments, at least300° F. for at least 2 hours. The repair agent remains strong enough torepair the laminate after impact of 5 to 50 joules to about 70-80% ofthe non impacted control without any repair conduits. The repair occursin less than one hour. In some embodiments, the repair occurs in lessthan one minutes, or even in less than 30 seconds.

This disclosure is also directed to a chemical adhesive that has beendesigned to be used in a self-repairing composite system. The chemicalis a modifying agent or repair agent that can resist the heat ofprocessing of the composite, such as laminate processing conditions. Insome embodiments, the heat of processing is at least 250° F. for atleast one hour or at least two hours, and in other embodiments, is atleast 300° F. for at least one hour or at least two hours. Even afterprocessing of the composite, the modifying agent is preferably able tobeneficially survive subsequent high temperatures, and in someembodiments, moisture (e.g., liquid water) at the surface and/orinternally in the composite. In some embodiments, the modifying agent isalso designed to have an extended shelf life, prior to processing of thecomposite, subsequent to processing, or both.

The disclosure also provides systems having conduits comprising boronmaterials, either as the conduits or on the wall, which can be oxidizedat high temperatures in a carbon atmosphere. At very high temperatures,the boron melts, becoming flowable glass. As the melted boron isreleased from the conduit to repair the damaged areas, in the presenceof oxygen the boron reoxidizes into a material having highertemperatures than the boron before oxidation. This step wise increase intemperature and oxidation resistance can occur several times withseveral different boron on boron like materials.

In another aspect of this disclosure, a chemical adhesive is providedfor a laminate, the adhesive being a modifying agent that can react withmore than one part of a laminate, such as atmospheric air, the conduit(or a portion thereof) retaining the modifying agent, structuralmaterials in the laminate (e.g., graphite) or fillers or other materialsin the laminate (e.g., clay, carbon black, nanotubes, moisture, cement).In some embodiments, this modifying agent is temperature resistant,e.g., at least up to 250° F. for at least one hour or at least twohours, and in other embodiments, at least up to 350° F. for at least onehour or at least two hours.

In still another aspect of this disclosure, two conduits are provide forretaining a two-part system, which upon reaction, self-repairs orself-forms a matrix. Each conduit contains one part of the two-partsystem. The conduits could be any of tubes or fibers, channels, orbeads. Tubes or channels could be twisted or twinned or otherwise inclose proximity to each other.

In yet another embodiment of this disclosure, exotic reactions are usedfor self-repair systems. Exotic reactions include those that involveROMP (ring-opening metathesis polymerization), Bergman cyclization,Dehls Alder, Shrock chemistry, DCDP (dicyclopentadiene), Grubbsruthenium, tin and iron.

In some embodiments, the repair modifying agent in the self-repair orself-forming system is a one-part adhesive. In other embodiments, therepair modifying agent in the self-repair or self-forming system is atwo-part adhesive.

The present disclosure also provides a reactive system for a self-repairor self-forming system that is initiated with exposure to air. Thereactive system includes a repair agent or modifying agent, such asurethanes, other sealants or adhesives such as esters or cyanates whichmay react with moisture present in the air. In some embodiments, thisrepair agent or modifying agent is present in a repair conduit, untilreleased by rupture of the conduit.

In some embodiments, conduits, such as beads or tubes, may be made fromreactive materials, such as many adhesives or repair chemicals listed inthe ingredients list herein. The conduits may be made by putting them ina reactive substance to form a shell, and taking them out and stoppingthe reaction by exposure to another chemical.

Matrices that could be made with a self-forming system include polymericmatrices and cementitous matrices, for example, with hexamethylenediamine and acid such as maleic or succinic to make nylon 666 whichgives off water to react with cement.

The present disclosure provides for other ways of self forming matrices.Fibers filled with a one part repair chemical can have the other part onthe fiber surface and upon fiber breakage the two can react and combineand create a fiber resin matrix system. This could also be made into apre-preg system for later activation into a composite. Additionally theself forming system can use the same not emptied fibers for later selfrepair of the self formed matrix.

The self forming conduits with repair chemical inside and on the surfacemay be present as a three dimensional (3-D) system of fibers or channelsor a weave or array. Fibers may be provided as a dense woven or knittedmat, or be present as a lofty non-woven mat.

In alternate embodiments, the repair conduits may be present as a threedimensional (3-D) system of fibers or channels or a weave or array.Fibers may be provided as a dense woven or knitted mat, or be present asa lofty non-woven mat.

The present disclosure provides an energy circulation system in whichthere is no external mechanical element or special forms to provide, forexample, mixing of reactants, pumping of liquid, controlling fluid flow(e.g., valves). The circulation system with chemicals in a matrixsubject to damage energy includes, in situ, elements to produce energyflow and fluid flow within the system, without external mechanisms orspecial elements in form.

The present disclosure also provides an energy circulation system,comprising a modifying agent in a conduit in a matrix. After an impact,the modifying agent flows into voids in the matrix created by the impactin less than 2 second. In some embodiments, the modifying agent hasfilled the damages areas within one minute. In some embodiments, allflow has ceased within about one minute.

In some embodiments, the energy circulation system includes metals orother inclusions which can react in the matrix in response to damageenergy. Examples of metal inclusions include iron, aluminum and copper,and alloys and combinations of those materials or any other metal oralloy.

The present disclosure, in some embodiments, provides for the use of insitu release fibers designed as energy pumps in the self-repair systems.These fibers functioning as pumps can be impendence, osmotic, magneticor elastomeric, or pressure release pumping. The modifying agent isreleased from the conduits in response to a stimulus for self-repairwhich is transmitted through these conduit release fiber/tube pumps.

The disclosure also provides for the production of energy within theself-repair due to movement of a fluid inside the conduits, such asmagnetic tube system. Inclusions of magnetic spheres move and createmotion, which then increase the fluid motion and provide increasedcirculation throughout the system. Magnetism and motion can yieldelectricity. Magnetic spheres can be half positive and half negative forbetter mixing.

The disclosure also provides for the absorption of radar energy by thesystem, such as with glass spheres coated with ferrite all in a liquid.The ferrites absorb radar wave energy, which is expelled as heat energy.The ferrites can also move in the liquid to find the optimum angle ofthe radar incoming waves.

Also within this disclosure are various special applications such as forsensing of damage and repair, repair of cryogenic tanks exposure to lowtemperatures, articles which generate their own heat as computers andtires, and space applications in which low gravity and vacuums mayaffect and allow use of different chemical release systems.

Also within this disclosure is aerodynamic motion control, by the flowof modifying agent within the conduits The conduits, e.g., a weave orarray, contain liquid modifying agent which can flow with the motion tocreate aerodynamic changes which can act to control the shape or angelof the overall structure such as an airplane.

Also within this disclosure is a chemical adhesive for self repair ofcementitious articles. This chemical adhesive, as a modifying agent,reacts with an alkaline cementitous matrix when included in aself-repairing system. In some embodiments, the cementitious matrixincludes one or all of cement, calcium carbonate, silicates, water, sandand aggregates.

Also within this disclosure is a chemical adhesive for self repair ofcementitious articles which can resist or survive high temperatures ofcement hydration ad later in-field temperatures.

These and other embodiments and aspects are within the scope of thisdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematic views of a self-repairing matrix compositematerial, illustrating various stages of matrix repair sequence ofload-induced cracking, modifying chemical release and subsequent repairof the matrix and rebonding of the fiber;

FIGS. 2A and 2B are schematic views of a composite material including amatrix with randomly dispersed repair fibers;

FIGS. 3A and 3B are schematic views of a laminate composite materialincluding a matrix with a layer of oriented repair fibers;

FIGS. 4A and 4B are schematic views of a self-repairing matrix compositematerial, illustrating release and repair from twisted fiber bundles,whereby compressive loading causes unlocking of the twisted fiberbundles to release modifying agent into the adjacent matrix;

FIG. 5 is a schematic rendition of an embodiment of a self-repairingdynamic system;

FIG. 6 is a schematic illustration of a first in situ osmotic pumpformed by a repair conduit of a self-repairing system;

FIG. 7 is a schematic illustration of a second in situ osmotic pumpformed by a repair conduit of a self-repairing system;

FIG. 8 is a schematic illustration of a repair conduit of aself-repairing system producing an electric field, which causes fluid topump;

FIG. 9 is a schematic illustration of a repair conduit of aself-repairing system producing an electric field, which causes fluid topump;

FIGS. 10A and 10B are schematic renditions of a repair conduit with theconduit having one part of a reagent inside and a second part of areagent outside of the conduit as a coating, upon breakage of theconduit the two chemical react forming a chemical matrix; and

FIG. 11 is a schematic rendition of the prior art self-repair systemhaving pumps and valves for moving the modifying agent therethrough,tubes in many layers and mixing towers.

DETAILED DESCRIPTION

The present disclosure provides various solutions and elements to solveproblems associated with the prior art. The repair system of thisdisclosure provides in situ energy management within the shapedcomposite, regulating dynamic fluid flow, energy flow and chemicalreactions within the composite over time. The present disclosureprovides various elements, such as processing of the products underheat, development of adequate repair chemicals in terms of heatresistance, speed of repair, and simple in-situ systems which use theenergy and chemical flow in a circulation system to repair well, systemsto repair medium to high impact damage, fatigue damage, as well as selfforming/self repairing composites as well as other multiple functionapplications. This disclosure provides, for example, the use of smallerrepair conduits, the use of integral channels as well as separate repairfibers, and the conduits could be woven, interwoven or nested with otherrepair fibers or with reinforcing fibers. This disclosure also providesimproved modifying agents, one-part and two-part, improved uses, andimproved methods of incorporation into the matrix. The modifying agentscan include additives for heat stability, shelf file, water resistance,etc.

In the simplest form, in order to be self-repairing, a special modifyingagent is stored in a conduit embedded in a matrix. When the resultingcomposite is damaged, the damage progresses through the compositematrix, breaking the conduit and releasing the modifying agent. Themodifying agent flows into the crack and re-bonds the cracked ordelaminated faces.

Referring to the figures, and particularly to FIGS. 1A-1D, aself-repairing matrix composite and its operation in the field isschematically illustrated. As depicted in FIG. 1A, a shaped article isformed having a hollow repair conduit, such as a fiber, containing amodifying agent therein and optionally coated with a thin coatingmaterial. The repair conduit is dispersed within a settable or curablematrix material, which may be either a polymer or cementitious material.In FIG. 1B, a load applied to the shaped article causes strains withinthe matrix, which in turn cause the repair conduit to break (FIG. 1C)and the matrix to crack. This causes the modifying chemical agent withinthe hollow repair conduit to be released into the vicinity of the crackin the matrix as shown in FIG. 1B. The modifying agent flows and fillsthe void as shown in FIG. 1D and cures to rebond the fiber to the matrixand to repair the fiber to itself. This schematically illustrates themodified fiber concept of the present invention.

The self-repair system is improved over previous systems in that one ormore of the following traits are seen in composites, includinglaminates, incorporating the self-repair system of this disclosure:

(1) the repair system can withstand processing temperatures in a rangefrom no heat (e.g., ambient conditions) to 250° F., 300° F., or 350° F.for several hours, and the resulting composite can withstand hightemperatures without damage to the repair system;

(2) the repair system can repair the large scale damage generallyexperienced with laminates such delaminations as may occur in stronggraphite laminates, as well as smaller size damage as in fiberglasslaminates;

(3) the repair system can repair impact damage caused by fast and largeimpacts or forces, as well as slower and lower forces such as fatiguedamage, structural cycling, thermal cycling, movement cycling, and creepdamage;

(4) the repair system can repair damage in a controlled manner, withinless than one minute or up to several days, as desired; and

(5) the repair system provides in situ energy management, regulatingdynamic fluid flow, energy flow and chemical reactions over time.

The following descriptions of the various components of the self-repairsystems of this disclosure provide a background for the later, detaileddiscussions. It should be understood that the following paragraphs donot limit the later discussions nor are the later discussions limited tothe materials provided here. It should also be understood that althoughspecifics or elements have been provided in respect to one of theembodiments or methods, that all the specifics and elements can be usedinterchangeably throughout the teachings of this disclosure, asappropriate.

Uses for Technology

The shaped articles or composites disclosed herein or made by themethods disclosed herein can be used in any number of goods. Examples ofuses for the composites include in materials such as those used inconstruction, building, roofing, roadway, industrial, aircraft,automotive, marine, appliances, recreational, electronic goods,transportation and/or biomedical fields.

Examples of construction, building, roofing or roadway uses includecement, concrete, phosphate cements, roads, infrastructure,earthquake-resistant buildings and other structures, bridges, tunnels,and pothole repair.

Examples of industrial applications include filament wound cryogenictanks, cryotanks to resist hydrogen, oxygen, nitrogen, other gases, atvarious temps, cryotanks for laser systems, thermally cycled bonds,adhesively bonded joints, nuclear power plant towers, oil rigs andpipelines, power grids, gas pipes, concrete girders, reinforcingtendons, structural composites, windows, and containment structures forradioactive or chemical wastes.

Examples of aircraft, automotive, marine and other transportationapplications include tires and tire parts, boat and submarine hulls,airplane hulls and wings and other structures, helicopter structuresincluding rotor blades, space vehicles and satellites, automotive bodyand frame parts, truck trailers and tanks, and engine pistons.

Examples of recreational applications include golf balls and clubs,bicycles, hockey and lacrosse sticks, tennis rackets, bats, helmets,armor, padding and other safety equipment, goalposts and net supports,pleasure craft, and floatation devices.

Examples of electronic goods include electronic packages, printedcircuit boards (PCBs) and PCB laminates, electronic encapsulants,electronic die attach, and housings for computers, computing devices andother electronic goods.

Examples of biomedical applications include bone grafts and natural bonegrowth, implants, prostheses, smart-release bandages, artificial skinmaterials, poultices and the like which include additives which releasehealing chemicals or healing promoting chemicals by upon movement of thepatient or by application of another stimulus, such as for example, aheating pad, or the like. The composites used in these bandageapplications might include such release chemicals as oxygen releasingchemicals, moisturizers, aloe vera, antibiotics, anti-inflammatants,analgesics, non-stick agents or the like.

The self-repairing composites could also be used for other miscellaneousapplications such as pipe repair, rubber matrices, plastic packaging,adhesives, impregnating resins, and paints, finishes, sealants andcoatings, which could be scratch resistant.

In some embodiments, the self-healing composites, when polymeric based,have a flexural modulus of from about 2,000 to about 200,000 psi.

Matrix

As provided above, the basis for the composite materials is a matrixmaterial, which can include any curable, settable material. Typically,these materials are moldable or castable to form shaped objects or maybe laminated or may be laminated or assembled into finished products,such as those listed above.

The matrix can be organic or organic based. Examples of matrix materialsinclude polymeric materials, cementitious materials, and polymericceramic matrix. In some embodiments, the matrix may be self-forming,from materials present within conduits, as is described below.

A polymeric matrix can include thermosetting resins, thermoplastics, andelastomers. Thermosetting resins include temperature-activated systems,polymerization agent-activated system, and mixing-activated systems. Thethermoplastics can be noncrystallizing thermoplastics or crystallizingthermoplastics. Examples of thermoplastics that can incorporate theself-healing system include olefinics, vinylics, styrenics,acrylonitrilics, acrylics, polyacrylates, polycarbonates, polyalloys,cellulosics, polyamides, polyaramids, thermoplastic polyesters andcopolyesters, polyethers, phenol-formaldehyde resins, amine-formaldehyderesins, poly(acrylonitrile-butadiene-styrene), polyurethanes includingfoaming polyurethanes, polyolefins, polysilanes, sulfones andpolysulfones, polyimides and imide polymers, ether-oxide polymers,ketone polymers, fluoropolymers, and heterochain polymers, and the like.Additional examples of thermosetting resins include, for example, epoxysystems (both one-part and two-part systems), formaldehyde systems,urethane/urea systems, formaldehyde systems, furan systems, allylsystems, alkyd systems, unsaturated polyester systems, vinyl estersystems, and the like. Epoxy systems include cycloaliphatic epoxies,diglycidyl ether of bisphenol-A or its brominated versions,tetraglycidyl methylene dianiline, polynuclear phenol epoxy, epoxyphenol novolac, epoxy cresol novolac, hydantoin epoxies, and so forth.Epoxy resin systems can be processed in a variety of manners and can becured at low or elevated temperatures. Formaldehyde systems includeurea-formaldehydes, phenol formaldehydes, and melamine formaldehydes.

Elastomers that can be enhanced by this invention include vulcanizableelastomers, reactive system elastomers and thermoplastic elastomers.Examples of such elastomers include diene and related polymers,elastomeric copolymers, ethylene-related elastomers, fluoroelastomers,silicone polymers, and thermoplastic elastomers. Thermoplasticelastomers can include rubbery polymers and copolymers including, forexample without limitation, styrenebutadiene rubber (SBR), neoprene,EPDM and silicone rubbers and the like.

Examples of thermosetting materials that can be used as a matrix withthe self-repair system include acrylates, methacrylates, cyanoacrylateresins, epoxy resins, phenoplasts such as phenolic resins, aminoplastssuch as melamine-formaldehydes, unsaturated polyester resins, vinylester resins, polyurethanes, and so forth.

Low viscosity resins can be cast. Molding compounds can be injectionmolded, compression molded, or transfer molded.

Concrete, cement, phosphate cements, sintered fly ash or bottomash/phosphoric acid mixtures, and asphalt are also common matrices forthe self-repair system. The system is particularly suited to withstandsurvive field mixing, placement of the repair conduits in or under thetop of such articles so that future impact, shear cracking, fatigue,creep and drying shrinkage damage can be repaired.

The matrix materials may be cured by means of catalysts, crosslinkers,radiation, heat, laser beam or by any means used with monomers reactingwith resins or polymers in the art for setting up, hardening,rigidifying, curing or setting these matrix materials to form shapedarticles or objects. The matrix compound should be formulated tominimize any potential inhibiting activity by it relative to themodifying agent.

Repair Conduits

Throughout the matrix are distributed the repair conduits. The repairconduits can be any suitable structure that provides a vessel forreceiving and retaining modifying agent until ruptured and released. Inmost embodiments, the repair conduit has an internal volume forreceiving and retaining the modifying agent. The structure of the repairconduit should be such to adequately rupture or break to release themodifying agent.

Examples of fibers that can be used as repair conduits include hollowoptical fibers, glass tubes, glass pipettes, carbon fibers, straws, andthe like. Fibers have an internal volume that can be defined by asurrounding wall. The fiber can be filled with modifying agent prior toor subsequent to incorporation into the composite. Some typicalmaterials for fibers include glass, polymeric or plastic, fiberglass,quartz, carbon and metal. Other typical materials for fibers includehydrous metal oxide, silica, silicates including borosilicates, silicon,and silicate type sol-gel precursors. Examples of typical organic fibersinclude polyolefin fibers, polypropylene fibers, polyester fibers,polyamide fibers, polyaramid fibers, urea-formaldehyde fibers, phenolicfibers, cellulose fibers, nitrocellulose fibers, GORTEX fibers, andKEVLAR fibers. Glass fibers and similar are preferred because of theease of melting, bending, and forming; for example, the ends can bemelted to be sealed.

Fibers may be rigid or may be flexible and/or bendable. For example, thefibers may be sufficiently flexible insert into pre-pregs, tows orweaves and yet be breakable. Multiple fibers could be woven to provide amat of repair conduits.

In some embodiments, the fibers may have a coating or other surfacetreatment to modifying the fiber properties. For example, a coating orother surface treatment may be present to inhibit compromise of themodifying agent, such as by the fiber material. The fiber interior orexterior could be coating with, for example, metal or carbonyl ironferrite. Radar waves induce alternating magnetic fields in carbonyl ironferrite which causes conversion of their energy into heat. As anotherexample, the interior surface of a fiber may have a coating to reducesurface tension, thus increasing capillary flow along the surface. Asanother example the interior or exterior coating may be metal to allowan electrical current to flow along the fiber.

Volumes void of matrix, e.g., channels, can be formed (e.g., integrally)in the matrix and used as repair conduits for retaining and releasingmodifying agent. Such channels have an internal volume defined by thematrix itself. The channels are generally filled with modifying agentafter incorporation into the composite. In some embodiments, asacrificial fiber or tube may be used to form the channel. Upon acondition, for example heating, the sacrificial tube or fiber may meltor otherwise disintegrate, leaving an empty channel.

The sidewalls of the conduits are typically rupturable or porous topermit the discharge or exiting of the modifying agent into thesurrounding matrix material upon the appropriate stimulus.

The repair conduits may be bundled, woven or loose. They may be held orengaged together with flexible web materials. They may comprise twistedpairs (as in FIGS. 4A and 4B) and additionally may include concentricstructures of one or more fibers. It is not necessary that the repairconduits have a single, elongate volume, as do the fibers and channelsdescribed above. Multiple fibers or channels could be interwoven andconnected to form an interconnected grid or matrix of conduits that hasone large volume. The pattern could be, for example, a honeycomb patternor a checkerboard pattern, having conduits positioned orthogonal to eachother. Such interconnected fiber structures have capillary channelstherein to allow the modifying agent to flow through the structure. Insome embodiments, the interconnected fiber structure is 3-D, with X-,Y-, and Z-direction fiber systems, thereby providing a system fordistributing the modifying agent uniformly through the matrix.

In addition, a plurality of hollow beads could be used as repairconduits.

The repair conduits, whether fibers, channels, beads or otherstructures, can be any desired size, length, have any wall thickness orcross-sectional configuration. In most embodiments, the repair conduitshave a diameter of 100-1200 micrometers. The conduits may be relativelysmall, chopped or comminuted fibers having lengths of less than aboutone inch and diameters of less than about 100 microns. The small size ofthe conduits is preferred so that they do not interfere with the actionof the composites, e.g., laminated composites, no matter where they arereinserted yet they should have sufficient volume to carry of modifyingagent to fill and repair cracks. Examples of suitable sizes of outsidediameter/inside diameter of fibers include 250/700, 500/850, 1000/1300,1000/1600 micrometers. In some embodiments, such as when two differentmodifying agents are used, or when the modifying agent is atwo-component system, two different sizes of conduits may be used.

Modifying Agent

Retained within the repair conduit is at least one modifying agent. Insome embodiments, the repair conduit is made from the modifying agent;i.e., the modifying agent forms its own shell, which acts as the repairconduit.

Typically the modifying agent is liquid, so that it readily flows outfrom the conduit. The modifying agent may be a one-part material thatself-reacts or two-part (or more) material. Generally for two-partmaterials, one part is present in the repair conduit and the second partis present in either the matrix or other repair conduits. FIG. 4Aillustrates two repair conduits in close proximity to each other; inthis embodiment, one conduit can include the first part of a two-partmodifying agent and the second conduit can include the second part.

Upon damage of the composite, the modifying agent is released from therepair conduit, moved around in the circulation system of theself-repair system, and chemically and/or energetically altered. In FIG.4B, the conduits are ruptured, so that the two modifying agents flowinto the damaged area, react together, and repair the area.

The modifying agent, present within the repair conduit, is selected frommaterials capable of beneficially modifying the matrix composite aftercuring. The modifying agents are selectively activated or released in orinto the surrounding matrix in use in response to a predeterminedstimulus be it internal or externally applied. In some embodiments,additional chemicals or secondary modifying agents are present in thematrix which can be pulled along and self polymerized or yield acontinual reaction.

The modifying agent may be a commonly available or simple chemical ormay be an ‘exotic’ chemical. Exotic chemical have reactions such asreactions involving condensation reaction polymers, ROMP (ring-openingmetathesis polymerization) reaction, Bergman cyclization or Diehls Adlerreactions. Some of these reactions are intended to not require mixingbut are fully consumed by the chemical reaction itself without outsideheat or mixing, they are autonomous.

The modifying agent is a polymerizable compound and can be a monomer,oligomer or combination thereof. Examples of polymerizable compoundsinclude acrylates including cyanoacrylates, olefins, lactones, lactams,acrylic acids, alkyl acrylates, alkyl acrylic acids, styrenes, isopreneand butadiene. The modifying agent can be an expoxide material, eitherone-part or two-part.

Suitable cyanoacrylates include ethyl cyanoacrylate, methylcyanoacrylate, b is 2 cyanoacrylate, cyanoacrylates with silicon,fluoroalkyl 2 cyanoacrylate, aryloxy ethyl 2 cyanoarylate,cyanoacrylates with unsaturated groups, trimethylsilyl alkyl 2cyanoacrylate, and stabilized cyanoacrylate adhesives, such as taught inU.S. Pat. No. 6,642,337 and U.S. Pat. No. 5,530,037.

Olefins include cyclic olefins, e.g., containing 4-50 carbon atoms andoptionally containing heteratoms, such as DCPD (dicyclopentadiene),substituted DCPDs, DCPD oligomers, DCPD copolymers, norbornene,substituted norbornene, cyclooctadiene, and substituted cyclooctadiene.Specific examples include, but are not limited to norbornene (such astriethoxysilylnorbornene, norbornene, ethyl norbornene,propylnorbornene, butylnorbornene, hexylnorbornene), alkyl-substitutednorbornene derivatives, and alkoxysilynorbornenes. Correspondingcatalysts for these are ring opening metathesis polymerization (ROMP)catalysts such as Schrock catalysts.

Lactones, such as caprolactone and lactams, when polymerized will formpolyesters and nylons, respectively. Corresponding catalysts for theseare cyclic ester polymerization catalysts and cyclic amidepolymerization catalysts, such as scandium triflate.

Still another class of modifying agents particularly useful in polymermatrices are solvents which permits solvent action to actually repairmicrocracking damage locally at a cracking site or possibly to dissolvethe matrix or fibers or both to permit them to re-form at a later time.

In addition to solvents, other curable monomers and co-monomers may alsoserve this repair function. pH modification agents may also be used asthe modifying agents, either alkali or acidic agents, which may beplaced in the interior of the fibers only to be released by anappropriate pH changes in the matrix. Other additives may include flameretardant agents. Visco-elastic polymers may also be used as modifiers.

The modifying agent may be a catalyst, which is a compound or moietythat will cause a polymerizable composition to polymerize, and is notalways consumed each time it causes polymerization. Examples ofcatalysts include ring opening polymerization (ROMP) catalysts such asGrubbs catalyst, and also other ruthenium, iron, osmium, rhodium,iridium, palladium and platinum. The modifying agent may alternately bean initiator, which is a compound that will cause a polymerizablecomposition to polymerize, and is always consumed at the time it causespolymerization. Examples of initiators are peroxides (which will form aradical to cause polymerization of an unsaturated monomer); a monomer ofa multi-monomer polymer system such as diols, diamines, and epoxide; andamines (which will form a polymer with an epoxide). In otherembodiments, the modifying agent may be a native activating moiety,which is a moiety of a polymer that when mixed or contacted with apolymerizer will form a polymer, and is always consumed at the time itcauses polymerization. Examples of a native activating moiety include anamine moiety (which will form a polymer with an epoxide).

Certain water barriers are particularly useful modifying agents forcementitious matrices. These may include special ZYPEX brand sodiumsilicate additives, as well as siloxane and silica additives known asSALT GUARD and the like.

No matter what the modifying agent used for the repair, one or moremodifying agents can be present in and/or on the repair conduit.

The modifying agent, in some embodiments, can resist high temperaturesof processing (e.g., 250° F., or 300-350° F.), boiling, have a longshelf life, and react fast (e.g., in less than one minute, and in someembodiments, less than 30 seconds). Additional details regarding hightemperature resistant modifying agents are provided below. One modifyingagent that is suited for high temperature processing is epoxy. Aspecific epoxy class that has been found to be particularly suited formoderate temperature processing is epoxy vinyl esters; such as thosecommercially available under the trade designation DERAKANE.

Means are provided for maintaining the modifying agent within the hollowfibers. The modifying agents may be physically trapped by, for example,drawing liquid additives into the interior of the fibers and retainingthem therein by capillary action or by closing off the ends of thefibers.

Structural Reinforcing Materials

The matrix typically includes, as needed or desired, dispersed thereinstructural reinforcing materials such as reinforcing fibers or fillers.These reinforcing materials generally increase any or all of tensilestrength of the composite, compressibility, toughness, ductility, andthe like.

Examples of commonly used fiber reinforcements include silica fibers,glass fibers, polymeric fibers (including nylon, aramid, polyolefin,polyethylene and polypropylene), carbon fibers, ceramic fibers, andmetal fibers. Fiber reinforcements may be present as individual fibers,as yarns or threads, or as mats of multiple fibers.

Rebar is a common large-scale reinforcement for concrete matrices.

Examples of suitable reinforcing fillers include: metal carbonates (suchas calcium carbonate (chalk, calcite, marl, travertine, marble andlimestone)), calcium magnesium carbonate, sodium carbonate, magnesiumcarbonate), silica (such as quartz, glass beads, glass bubbles and glassfibers), silicates (such as talc, feldspar, mica, calcium silicate,calcium metasilicate, sodium aluminosilicate, sodium silicate), metalsulfates (such as calcium sulfate, barium sulfate, sodium sulfate,aluminum sodium sulfate, aluminum sulfate), gypsum, vermiculite, woodflour, aluminum trihydrate, carbon black, certain metal oxides (such ascalcium oxide (lime)), alumina, tin oxide (e.g. stannic oxide), titaniumdioxide, metal sulfites (such as calcium sulfite), thermoplasticparticles (e.g., polycarbonate, polyetherimide, polyester, polyethylene,polysulfone, polystyrene, acrylonitrile-butadiene-styrene blockcopolymer, polypropylene, acetal polymers, polyurethanes, nylonparticles) and thermosetting particles (such as phenolic bubbles,phenolic beads, polyurethane foam particles). Other miscellaneousfillers include sulfur, organic sulfur compounds, graphite, boronnitride, and metallic sulfides. The above mentioned examples of fillersare meant to be a representative showing of some useful fillers, and arenot meant to encompass all useful fillers.

Of course many of the filler materials named above may also be used as arepair chemical encapsulants for example a hollow rebar in concretecould contain a repair adhesive, as can porous aggregates. That is, theymay act as functional additives. Other inclusions may have a significantrole in self repair such as metal particles which could heat the matrixand cause self repairing chemicals to chemically react.

Functional Additives

The matrix may include, as desired, any number of optional additivesthat modify or affect the properties of any one or more of the repairconduit, the modifying agent, the matrix, and their interactions witheach other. A mere sampling of suitable functional additives is providedbelow.

Examples of clays include silica clay, green clay, kaolinite, bentonite,montmorillite, and nanoclays.

Examples of commonly used inclusions include metal powders, glassflakes, mica, aluminum flakes, alumina trihydrate, calcium carbonate,carbon black, solid microspheres and hollow microspheres.

Examples of conductive or semi-conductive particles include carbon;carbon black; graphite; silicon; silicon carbide; III-V semi-conductingmaterials including gallium arsenide, gallium nitride, galliumphosphide, gallium antimide, aluminum antimide, indium arsenide, indiumphosphide, and indium antimide; II-VI semi-conducting materialsincluding zinc oxide, cadmium sulfide, cadmium telluride, zinc sulfide,cadmium selenide, zinc selenide; and IV-VI semi-conducting materialsincluding lead sulfide and lead telluride.

Metal particles include iron, tin, zinc, aluminum, beryllium, niobium,copper, tungsten, silver, gold, molybdenum, platinum, cobalt, nickel,manganese, cerium, silicon, titanium, tantalum, and magnesium mixturesand alloys thereof; metal alloys such as steels and tool steels,stainless steels, plain carbon steels, low carbon steels,aluminum-nickel, brass, bronze; and alloys used for biomedicalapplications such as cobalt-chromium, cobalt-chromium-molybdenum,cobalt-chromium-tungsten-nickel,cobalt-nickel-chromium-molybdenum-titanium, andtitanium-aluminum-vanadium alloys.

Optional Additives

The matrix or resulting composite can include optional additives suchas, for example, UV stabilizers, heat stabilizers, antioxidants,colorants, flame retardants, anti-corrosion chemicals, anti-freezematerials, antimicrobials, odorants, surface-modifying additives,processing aids, coupling agents, viscosity modifiers, pH modifiers,plasticizers, and/or bulk modifiers.

In addition these additives could be released also as a chemical tobeneficially enhance the matrix.

Of course, other additives could be added to the composite, for anyreason. It is understood that although examples of specific materialsare provided in various classes, that these materials may provideadditional advantages to the matrix and/or composite.

Providing the Article

The composites having the self-repair system can be shaped into desiredshapes by any convenient technology, including, for example, lamination(such as form making fiber-reinforced plastics and structural compositesusing fiber preforms or fiber pre-pregs, and so forth), injectionmolding (such as for making microelectronic parts, watch components,locating pins, bushings, ribs, flanges, dashboards, outdoor furniture,and so forth), extrusion (such as for making sheets, pipes, fibers,pellets, and so forth), extrusion covering (such as for making sheathingfor wires and cables), film blowing (such as for making single ormulti-layer covers, and packaging applications such as wrap, can lining,bags, and so forth), calendering (such as for making flat films orsheets), sheet thermoforming (such as for making blister packs,individual containers, structural panels and liners, windows, skylights,and so forth), blow molding (such as for making packaging and storagecontainers), coating on a substrate (such as for films, tapes,structural skins, flooring, wall coverings, and so forth), rotationalmolding (such as for making open containers, seamless flotation devices,toys, structural components), casting (such as for making encapsulated,embedded or potted electronic parts), compression molding (such as formaking electrical and electronic goods, knobs, buttons, closures, eatingutensils, tire parts, and so forth), transfer molding (such as formaking complex or fragile polymeric products), and sintering andmachining.

The basic elements and ingredients provided above can be assembled toprovide composite materials with desirable properties. The preferredprocessing methods, additional matrices, modifying agents, conduits, anduses for the composites are described in U.S. Pat. No. 6,261,360, U.S.Pat. No. 5,989,334, U.S. Pat. No. 5,803,963, U.S. Pat. No. 5,660,624,U.S. Pat. No. 5,575,841, and U.S. Pat. No. 5,561,173, the entiredisclosures of which are incorporated herein by reference.

1. Self-Repair of Impact Damage in Composites in General

An opportunistic dynamic notion of materials is included in thisapproach of self-repairing materials. As such, it can go beyondself-repair and solve problems with new totally dynamic structures interms of their energy, design for material flow and chemical change ofthe materials, all over the time of the composite (e.g., creation tofinal destruction). Improved over prior self-repair systems andmaterials, the present invention provides new and improved structuralcomposite materials, including composite laminates, having aself-healing or self-repairing capability whenever and wherever cracks,delamination or other damages are generated. This new understanding ofthe dynamic aspect and potentialities of materials, e.g., the energy,flow of fluids and chemical reactions over time, provides improvedsystems.

In some embodiments, the energy of an impact is transformed and is equalto the energy to form the delaminations and fiber breakage and matrixcracking. In self repairing systems the energy of impact is transformedand is equal to the energy to form the delaminations and fiber breakageand matrix cracking as well as the energy of repair tube rupture andforce on the chemical pushing it out. This energy sum is matched in someproportion, preferably at 70-100%, by the energy of adhesive repair tore-attach the laminate layers, re-attach the broken fibers and thebroken repair tube. This can be measured by strength restoration asfracture toughness which measures the energy required to pull laminatesapart, of compression of flexure. For example, about 5-50 joules areneeded to delaminate a 16-32 ply carbon composite laminate havinggraphite composite material and the repair with different repairchemicals can be 70-94%.

These systems for self-repair of impact damage in composites andcomposite laminates (e.g., graphite and fiberglass laminates) includeschemicals that are able to withstand the heat of processing, e.g., atleast 250° F. and at least 350° F. Additionally, the systems are able torepair quickly (e.g., in less than one minute). The repair system may bea one-part or two-part system designed to withstand levels of impactappropriate for the application (e.g., high strength graphite).

The present disclosure is to composite matrix, including laminates,having a plurality of hollow repair conduits dispersed therein, amodifying agent present, at least, within the repair conduits and/orthereon. Two examples of repair conduits are hollow repair fibers andchannels. Upon a predetermined stimulus, the modifying agent is releasedfrom the repair conduits into the matrix material. The matrix and therepair conduits together form an in situ fluidic system that transportsthe modifying agent(s) throughout the matrix.

In many embodiments, the matrix, including the modifying agent andrepair conduit, is particularly suited for use in or processing underhigh temperature applications, e.g., at least 250° F., often 250-350°F., for extended periods of time, such as 1-2 hours. In some of theseembodiments, the modifying agent is sufficiently heat stable towithstand the high temperatures. In embodiments where the stability ofthe modifying agent under high temperatures is questionable, themodifying agent can be applied to the fiber after the high temperatureprocessing. In most embodiments, the resulting article can withstandheat of use of the article and can also withstand any heat generated byenergy production in or by the article during use.

Means are provided for maintaining the modifying agent within the hollowconduits. The modifying agents may be physically trapped by, forexample, drawing liquid additives into the interior of the conduits andretaining them therein by capillary action or by closing off the ends ofthe conduits. As described later below, pump(s) conduits may be used topull or push the modifying agent out of the conduit.

Means are also provided for permitting selective release of themodifying agent in response to the external stimulus. Illustrativeexamples include cracking, breaking, bending or otherwise breaching thewall of the conduit, for example, by selectively removable ordissolvable coatings which give way to permit leakage of the modifyingagent in response to, for example, stimuli such as very high heating,cooling, loading, impacting, cracking, water infusion, chlorideinfusion, alkalinity changes, acidity changes, acoustic excitation, lowfrequency wave excitations, hydrostatic pressure, rolling pressure,light sensitivity or laser excitation, thermal, load cycling or thelike. Electrical currents, voltages, electrorheological excitation,radiation, or other energetic stimuli may also be employed or effectiveto permit or cause selective release of the modifying agent or agentsfrom the fibers.

The selective release of the modifier occurs in the matrix when andwhere it is required and may lead to improved toughness, strength,ductility, brittleness, permeability, fire retardancy, stiffness,dimensional stability, modulus of elasticity, fatigue, impactresistance, and other improved properties of the matrix composite. Theselective release of the modifying agent may be chosen to be effectiveto rebond the conduits to the matrix, to repair the conduits themselves,to improve or restore the matrix to conduit interface, to repairdelaminations, and to repair microcracks in the matrix itself which mayrepair or overcome cracking or corrosion induced dimensional weaknessesand ultimately reduced durability for the shaped articles.

It is known that alkali reactions are sometimes caused withincementitious matrix materials when aggregate reacts with matrix andcauses an expansion of the aggregate against the matrix. This causesinternal stresses to develop within the matrix composite or shapedarticle, which usually appears as cracks within the matrix. The use ofthe self-repair system with modifying agent in conduits will repair someof these cracks. In addition, instead of adhesives, the conduits may befilled with pH modification agents such as acidic agents to neutralizethe alkali reaction. In addition, conduits filled with the alkalireaction inhibiting acidic modifying agent may be used in combinationwith the matrix repair adhesive filled conduits.

Self-healing may be accomplished by leaving some of the originalconduits void or by adding additional conduits designed with specialtyrepair agents for repairing the system. Hollow porous conduits may beused to deliver repair agents at a later time if damage such as crackingoccurs. Repair modifying agents, either present as an adjuvant conduitadditive or added to conduits from the outside, may be used to improvethe visco-elasticity of the entire component as desired.

2. Self-Repair of Impact Damage in Laminates

The present disclosure provides self-repair of impact damage incomposite laminates, for example, graphite and fiberglass laminatesformed from pre-impregnated layers (i.e., pre-pregs). In most cases,this damage is in the range of 5 to 50 Joules, but could be higher orlower. It is believed that the maximum load or peak contact force,energy-to-maximum load, total energy, and deflection-at-maximum loadincreases parabolically with an increase in impact energy level, whereastime-to-maximum load or impact duration at the peak load decreaseslinearly.

In many embodiments, to obtain self-repair system that meet the desiredcriteria, this includes using developed chemicals that can withstand theheat of processing for laminates, e.g. at least about 250° F., and often350° F. The self-repair system is designed to withstand the levels ofimpact appropriate for high strength laminates, such as graphitelaminates, and repair quickly after damage has occurred.

Referring to FIGS. 2A and 2B, a layered laminate is illustrated. Inthese figures, one layer including individual repair conduits therein.The other two layers would typically include reinforcement materials,such as reinforcing fibers. FIG. 2A shows the laminate intact, prior toany damage.

A laminate composite article includes at least two layers or plies ofmaterial, usually at least four layers. Up to 100 layers, or more, canbe used in laminates. For some applications, laminates having 24-32layers are preferred. Typically, the strength, toughness and rigidity ofthe laminate increase as the number of layers increases, however, sodoes the weight of the laminate.

For impact damage self-repair of laminates, the forces caused by theimpact break the repair conduits and force the modifying agent into thedamaged site within less than a second. No pump or other mechanism isneeded to move the modifying agent, as simple pressure differencesbetween the repair conduit interior and the void in the laminate causedby the impact forces the modifying agent to the damaged site. Nomechanical valves are needed, as the modifying agent fills the voids andthen stops flowing out of the conduits when the pressure differentialhas lessened.

When a one-part modifying agent is used, no mixing required. Themodifying agent readily reacts with the laminate layers (e.g., thepre-preg). For a laminate (i.e., a multilayer structure), only one layerneeds to include the repair conduits, as the modifying agent readilyflows along the layer interfaces, including up against gravity, when animpact occurs. Additionally, the voids and broken reinforcing fibersthemselves provide conduits for flow to damaged areas. FIG. 2Billustrates a damaged laminated with modifying agent flowing to fill thedamaged area.

FIG. 5 illustrates an alternate embodiment with one layer of repairconduits in a laminate. In this self-repair system, (1) pumping occursby impact force affecting the repair conduit, a basic impedance pumprequiring no mechanical parts, (2) there is a one part modifying agentwhich requires no mixing, (3) only one layer of repair conduits is usedbecause the repair conduits break and allow the modifying agent to rushinto damaged areas, and (4) valves are not needed to push or halt theflow of modifying agent.

A second active agent, in addition to the modifying agent(s), could beadded to the system. This second active agent could be selected tobenefit the composite structure at a different time, separate from thedestructive impact.

Overall, the whole laminate acts as a circulatory microfluidic device.This is in keeping with the biomimetic principles of keeping the designsimple and the source of energy intrinsic.

3. Self-Repair of Fatigue Damage

The present disclosure provides self-repair of non-forceful damage suchas fatigue and thermal cracking that might occur over time a material.In such designed composites, integral channels within the matrix arepreferred, although fibers would also be suitable.

Embodiments are designed to withstand levels of impact appropriate forthe high strength graphite laminates and also for fatigue, thermalcycling and creep, which is a lower level force over longer time. Bothlaminates and single layer composites undergo fatigue, and thetechnology described herein can be used for both laminates and singlelayer composites.

The repair conduits may be present within the composite in a homogenousmanner (e.g., randomly distributed) or in a layer. FIGS. 2A and 2Billustrate a matrix having many repair conduits, with the conduitsrandomly distributed through the layers. This is a matrix such asconcrete, or a polymer matrix without a laminate structure FIGS. 3A and3B, illustrate a laminate having one layer of repair conduits. Inalternate embodiments, the repair conduits may be present as a threedimensional (3-D) system of fibers or channels or a weave or array or inlayers orthogonal to each other. Fibers may be provided as a dense wovenor knitted mat, or be present as a lofty non-woven mat. When pre-pregsheets are used, upon heating the resin from the sheets can readily flowand flow around the repair fibers thus incorporating the system ofrepair conduits into the laminate without much diminution in structuralproperties.

Low energy cracking or damage systems include applications such asbonded joints in electronics and cryogenic filament wound tanks. Inthese applications, the release of self-repair materials is elicited byservice loading conditions: thermal cycling in space environments,static creep and mechanical fatigue imposed by joint configurations, andresidual stresses due to mismatch of thermal expansion (bonded joints)or fabrication processes (filament wound cylinders). The self-repairsystem, particularly the modifying agent, must not cure or degradeduring thermal cycling over a temperature range that spans fromcryogenic temperatures to well above the typical composite curetemperature.

For fatigue environments, e.g., mechanical fatigue, thermal cycling andstatic creep, all of which can result in cracking that leads to crackpropagation, a different set of forces apply, as compared to impactenvironments. Often, the dynamic system fatigue is caused by less forceand repeated over a longer schedule of time. For a single layercomposite, the damaging forces would be in a smaller area or volume thanin a laminate.

The damage causes a space or void such as a crack to form in thecomposite. The damage also ruptures the repair conduit, which causes themodifying agent to at least ooze of flow out. As the modifying agentfills the void, it reacts, either by itself or with a second part.Generally, the modifying agent stops flowing when the space is filled orthere is no more pressure differential or void creation to push orattract the modifying agent out from the conduit.

Together, a total system is created, the system including the createdbreaks in the repair conduit, together with the cracks or voids in thematrix, ruptured conduits, and modifying agent migrating out of theconduits into the cracks.

4. Multifunctional Applications with Self-Repair

In some embodiments, it is desired to provide the self-repair systemswith additional properties in addition to the self-repairing properties.For example, repair conduits, e.g., hollow glass fibers, can be filledwith colored or tinted modifying agent which provides a color changeupon reaction, thus providing visual indication when the modifying agenthas been activated. In some embodiments, the electronic properties ofthe materials may be affected by the release of the modifying agent.

Electrically active or magnetic material (e.g., beads or particles,either solid or coated) could be used to create circulation energy,e.g., when retained in a fluid. Ferrite particles or a ferrite coatingcould be included to absorb radar energy and produce heat.

The ferrites can be positioned at various appropriate angles to theradar angle by the interaction of the charges on the individual magneticparticles. In general, the ferrites are free to move in a more activeway in a liquid modifying agent, the heat from the energy conversion canbe transported away via the in situ circulation system of theself-repair system, and the overall system can be multifunctional andself-repairing.

5. Self-Formation of Matrix

During a composite's life, the composite it formed over time, itfunctions over time and deteriorates over time, after which it may bethrown away. The composite may have various functions at the same time.A preferred composite is a multifunctional system in matrices withrepairing modifying agent that can withstand the heat of processing andany other heat of uses. It is efficient to envision materials which areplanned from formation, repair, function and disposal. This disclosureprovides methods of making materials (e.g., matrices) by using conduitsto both form the composite material and provide self-repair propertiesto it.

The preferred embodiment of a self-forming composite includes a totaldynamic energetic circulation system that functions as an in situfluidic system; for a laminate, this in situ fluidic self-forming systemis present in at least one layer or area. An impact or fatigue energy orother energies are delivered to the composite or laminate to causeenergies which in turn cause energy evolution and also creation of thecomposite structure. Usually subsequent to the forming of the composite,the energy self-repairs any damage to the composite.

At the same time (in impact or fatigue) or subsequently (in fatigue),failure energies or cracking of the conduit or coating release anyremaining modifying agent and the energies act as a impedance pump,pushing out the modifying agent. The void caused by the failure has anattractive force and the modifying agent flows into the void. The energyalso either mixes two-part modifying agents, pushes the modifying agentto the matrix walls, or causes the modifying agent to react with theforce alone or the force causes the modifying agent to react withparticles or causes particles to react.

In an embodiment of the invention, the modifying agent is a curablecomposition which reacts after release to cure within the matrixcomposition. The matrix composition includes a co-reactive componentwhich reacts directly with the modifying agent upon release of themodifying agent. Optionally, another co-reactive component can bedelivered or provided in the matrix which further reacts withby-products of a cure reaction of the modifying agent, e.g., forsubsequent damage repair.

In various embodiments wherein the curable matrix composition has atleast one curable monomer, the modifying agent may be a reactiveco-monomer, crosslinking agent, hardening agent, crosslinking catalyst,or a mixture of any of these which is capable of affecting the rate orparticipating in a cure reaction of each curable monomer. In someapplications, the modifying agent may be coated on the outside of thefiber.

Repair conduits may be used to influence curing through thermal means.Such a system is particularly suitable for affecting curing of thickmaterial sections more quickly or in any curing matrix formation whereinthermal control is desired, such as to prevent cracking from thermalstress due to nonuniform or excessively fast curing. Other compositionreactive agents can be actuated by heat. To this end, a method formaking an article includes providing a plurality of hollow conduitssurrounded with a shapeable curable matrix composition. Atemperature-enhancing fluid, such as a coolant, steam or other heatingfluid, is introduced or flowed into the interior portion of at least oneof the hollow conduits. Heat is thereby transmitted or absorbed from theintermediate portion of the hollow conduit into the curable matrixcomposition to either initiate or influence time of curing of the matrixcomposition and the modifying agent into a shaped matrix compositematerial.

Different conduits could be used for retaining and releasing modifyingagents having different functions or intended to be released atdifferent times. For example, a first conduit could be used forformation of the pre-preg, and a second conduit for later self-repair.Still additional conduits could be used for desired qualities, such asoptical sensing. In some embodiments, conduits may be present thatretain no modifying agent, but act only as reinforcement or filler. Insome embodiments, conduits or other fillers or fibers could be used toproduce energy, such as heat.

By encasing the modifying agent in repair conduits, this self-repairsystem permits more efficient use of materials in the self-healingcomposite. In some applications, even a single repair conduit withmodifying agent may be adequate for healing. In addition, by placing themodifying agent on specific surfaces, versus a dispersed second phase ofhomogenous modifying agent, this technique permits engineering of theself-healing reaction directly on the surfaces of reinforcementmaterials that might be present to further blunt or divert crack growth.

In some designs, second active agent, in addition to the modifyingagent(s) and its reactant, could be added to the conduits, e.g., a 3-Dsystem of conduits, to benefit the structure at a later time. It couldbe used to wet the conduits of the original structure and then also stayin the conduits to act as a self-repairing material at a later time.

In preferred embodiments, the modifying agent should be able to resistthe high temperatures of the processing for formation and later heating,so that the composite can later self-repair. For example, such as whenthe composite is combined with a regular pre-preg which is processed athigh temperatures of 250° F. and 350° F., such as for 1 to 2 hours ateach temperature.

As an example, a laminate using pre-preg materials can be made withhollow conduits having a two-part modifying agent system with onecomponent inside the repair conduit and the other on the outside, or aone-part modifying agent system with the component on the inside. Themodifying agent can be activated by release from the inside the conduitto react with the chemical on the outside make a composite or to make apre-preg for even later full activation. Additionally, after formationof the shaped article, an amount of the modifying agent may remainunreacted, available later for self-repair. Solvent may remain, waitingto be released from the conduit for later destruction and/or disposal ofthe article.

In some embodiments, a co-reactive component can be delivered orprovided in the matrix which further reacts with by-products of a curereaction of the modifying agent. For example, the heat of the initialcuring reaction can activate a heat-activatable component to cause asecondary reaction. An example of such a self-forming matrix is apolymer ceramic composite, made by the following procedure. A mass ofcement powder matrix, with appropriate sand and/or aggregate, iscombined with a resin reactant, such as malic acid or maleic or succinicacid. A second part of the resin reactant, such as hexamethylenediamine, a liquid, is supplied in conduits. Upon rupture of theconduits, the modifying agent flows from the hollow conduit to thepowders. The two resin reactants, i.e., the hexamethylene diamine andacid, react via polymer condensation reaction, forming nylon and aby-product, water. The resulting water hydrates the cement, formingconcrete. Another example of such as self-forming matrix can includenon-biological but biomimetic materials, wherein a polymer matrixcontaining crystallizable mineral elements such as alumina alkoxide maybe provided. A condensation reactive element or ingredient providedinside the self-repair conduits may be released on application ofappropriate external stimulus from the conduits within the matrixcontaining the alumina crystals. The by-product water of thecondensation reaction in this case may be used to cause alumina crystalsto grow at specified locations within the shaped article.

In various embodiments wherein the curable matrix composition containsat least one curable monomer, the modifying agent may be a reactiveco-monomer, crosslinking agent, hardening agent, crosslinking catalyst,or a mixture of any of these which is capable of affecting the rate orparticipating in a cure reaction of each curable monomer.

Also, a one-part matrix component may be provided through some or all ofthe conduits. The one-part component permeates through the conduit wallsand enters and optionally surrounds the matrix. The one-part componentcan be a simple adhesive, however, the one-part component preferablycomprises a liquid compound, e.g., epoxy resin, containing a latent orinert catalyst component. This latent catalyst is activatable by asuitable external stimulus. For example, the latent hardener componentmay be a light-activatable photoinitiator stimulated by light, aheat-activatable component activatable by a heat source such as a laser,a radiation-activatable component activated by ultraviolet, electronbeam, or gamma radiation. The external stimulus breaks down the inert,latent agent into activated catalyst to initiate curing. The latentcatalyst or modifying agent may also be delivered through a conduit at adelaminated location or through a break in a conduit caused by a breakor crack in the composite structure.

The conduits could thermally influence a matrix, such as during curing.It is recognized that some curing reactions such as polymerization cangenerate a substantial amount of heat. Particularly in conventionalthick-section composite formations, heat is not efficiently dissipatedand can build to excessive levels. If the heat exceeds the thermalstress limits of the matrix composition, the material can be damaged bycracking and weakening. Such damage may also result by uneven curingrates within the composite formation.

In some embodiments, the conduit is a conductor, such as metal, whichcan be charged by a voltage source in order to achieve a migration ofions through a curing composite structure. The metal conduits may haveholes located in their walls to deliver initiator, repair, or thermalfluids.

6. Dynamic Matrix

The self-repair system, and especially the self-forming matrix, isprovided by a series of chemical reactions to form a composite materialin which a modifying agent, either a one-part or two-part system, ispresent as a fluid in a solid matrix. Upon damage, the solid is brokenand the modifying agent(s) mix with the matrix, thus forming a solid ora fluid that then becomes a solid by a reaction. The purpose of thereaction is to repair damage such as cracks, voids, or delamination.

The self-repair systems of this disclosure provide a dynamic matrixmaterial which is transformed by external forces (such as impact) inwhich the conduit and modifying agent are present within the matrix torepair the matrix or provide the matrix itself. The resulting matrix mayreact to any result caused by impact, such as chemical melting due tochemistry, heat causing flow, reaction, etc.

The dynamic self-repair system relies on a system of liquid flows,energy applications and response and chemical reactions in asynchronized way. The energy in the system, either chemical or physicalmovement, may come from any of the aspects involved, such as the forcecaused by the impact or fatigue, the breaking of the conduit, a coatingon the conduit that initiates the formation of chemical energy, themodifying gent (which can be in several parts and in several locationssuch as in the repair conduits and throughout the matrix), inclusions inthe matrix (such as optional beads or particles), the matrix itself, theinteractions of various factors such as flow, the energy produced byflow, and the material properties themselves.

In other words, any aspect of the overall dynamic system may beresponsible for the remedial, beneficial, or repair action such as (1)the force combined with the modifying agent, (2) the heat of the forcecombined with the modifying agent, (3) the chemistry of the matrixitself, (4) inclusions in the matrix, (5) excess reactivity in thematrix that reacts with the force, (6) modifying agent that reacts withheat, or (7) leftover modifying agent is activated by environmentalintrusion (e.g., moisture). In general, the dynamic matrix material istransformed by external forces, either by formation of the matrix orrepair of the matrix.

The self-repair system is a total three dimensional composite systemthat functions as a dynamic circulation system in at least one layer(for a laminate) or area (for a single layer composite). The interactionof the various components provides a system that functions on its ownenergy. The force of the damage to the composite creates a damaged spaceor void, such as a crack or delamination. This damaged area draws themodifying agent out of the conduit, acting as an impedance pump orproviding suction. Also, the modifying agent flows out from the brokenconduit. Heat may be created by the reaction of the modifying agent; themodifying agent stops moving when the damaged space is filled or thereis no more pressure differential to push or pull it out of the conduit.The total system is one of created breaks in a composite or matrix,voids in the matrix, broken conduit and modifying agent flowing from theconduit and out into the damaged areas.

The self-repair system includes a total dynamic energetic circulationsystem that functions as an in situ fluidic system. The impact orfatigue energy or other energies are delivered to the composite orlaminate to cause failure initiation energies which in turn cause damageevolution and failure in the composite structure. At the same time (inimpact or fatigue) or subsequently (in fatigue), failure energies orcracking of the conduit or coating release the modifying agent and theenergies act as a impedance pump, pushing out the modifying agent.Additionally, the void caused by the failure has an attractive force andthe modifying agent flows into the void. The energy also either mixestwo-part modifying agents, pushes the modifying agent to the matrixwalls, or causes the modifying agent to react with the force alone orthe force causes the modifying agent to react with particles or causesparticles to react.

7. Magnetics and Radar Creating Energy

To further increase the energy in the dynamic, self-repair system, therepair conduits or other elements of the system can be configured to,directly or indirectly, create electricity or other energy. The dynamiccirculation system can have an adaptable energy producing self-repairsystem, which is caused by the flow of liquid (e.g., modifying agent) ina series of tubes (e.g., repair conduits). In some embodiments,electrically charged materials, moving inside of the conduits (e.g.,glass or magnetic fibers), creates additional energy; the conduit, orthe modifying agent itself may be charged or may carry chargedparticles. See, for example, FIG. 8. In other embodiments, in amagnetically charged conduit, the modifying agent within the conduit mayinclude magnetically charged particles, such as glass beads, in themodifying agent to create circulation and energy. Ferrite particles maybe used, which absorb radar energy and create heat. In some embodiments,the conduits may be metal, include metal inclusions, or have a metalcoating thereon. Magnetic tubes and magnetic particles which are half ofeach polarity cause dielectric current production; see FIG. 9. Themodifying agent can be driven around and out from the repair conduitwith an electrical field applied to a magnetic field from the conduit.

Any of the materials may be designed to carry color, change color whenelectronic properties are sensed, or to release a secondary chemical. Insome embodiments, the released modifying agent can provide an electronicsignal to the matrix.

The creation of energy (e.g., electricity) or heat can then be used toprovide further pumping of the modifying agent through the matrix. Themotion of the modifying agent may then give rise to additionalelectrical production. The presence of conductive modifying agentreleased into a matrix, such as a carbon matrix, can be read aselectrically conductivity matrix but with different resistivity than thematrix.

8. Pumps

A pump or series of pumps may be operably part of the conduit, typicallyto facilitate release from the conduit of the modifying agent. Examplesof useable conduit pumps and/or their inclusion into the system follows.An impedance pump, which is really a hollow fluid containing tube whichcan be impacted to siphon modifying agent from one place to another whenthe conduit is sharply hit. Conduit pumps such as elastic balloon pumps,can be used to release the modifying agent into the damaged area underpressure, thus when the conduit breaks, the modifying agent comes outvery quickly due to the pressure. Electronic pumps can be used; forexample, a solution of hydrazine sulfate is driven by electrolysis toproduce nitrogen and hydrogen (the mixing of the two chemical in aconduit would break the conduit and force the modifying agent out intothe damaged area). Vapor pressure pumps utilize a propellant gas in onechamber which liquefies when compressed, and drives the modifying agentin the other part out into the damaged areas.

Osmotic pumps, which have two chambers, might be present in the system.See, for example, FIGS. 6 and 7, wherein one chamber retains modifyingagent and a second chamber retains salt and is open to water. The waterwill flow into the salt chamber, swells in it, thus driving out therepair agent into the damage site. These are also known as Theeuwespumps. A magnetic system, in which small magnetic beads are dispersed inthe matrix, could be used. An oscillating magnetic field causes thebeads to compress the matrix, opening channels through which themodifying agent is released into the damage areas. A simple pressurerelease phenomenon can also be used as a pump. In this case the repairchemical is inserted into the conduit under pressure.

9. Additives to Modifying Agent or Reagent

In some embodiments of self-repair systems, the modifying agent has beendesigned to withstand, without degradation, processing temperatures in arange from no heat to at least 250° C. for at least one hour, and, e.g.,at least two hours. In some embodiments, the modifying agent is designedto withstand at least 300-350° F. for at least one hour and, e.g., atleast two hours. To provide the high heat resistance to the modifyingagent(s), various additives can be included to prevent damage duringheating and to prevent over heating and/or boiling.

It was found that adding an amount of certain additives, at a level ofat least about 1% to the modifying agent, provides improved heatresistance. Both one-part and two-part modifying agents benefit fromthese additives. Examples of suitable additives include cyclic organicsulfates, sulfites, sulfoxides, sulfinates, such as esters of sulfurousacid (e.g., 2-oxo-1,3,2-dioxathiolanes), hydroquinone, and antioxidants,e.g., phenolic antioxidant, such as butylated hydroxyanisole, includingbutylated hydroxyanisole (BHA; tert-butyl-4-hydroxyanisole) andbutylated hydroxytoluene (BHT; 2,6-di-tert-butyl-p-cresol), and thoseantioxidants available under the trade designation IRGANOX. Hydroquinoneand 2 ethyl hexyl methacrylate inhibit boiling of the modifying agent.In most designs, the level of the additive is between about 2-10%, andin some embodiments, about 4-8%.

Other additives could be added to the modifying agent to provideadditional or alternate characteristics. For example, sulfur dioxide maybe added to increase shelf life of the modifying agent (e.g., to 6months), plasticizers may be added to inhibit the material obtained frombecoming brittle. Chemicals which change color upon reaction could beadded.

In some embodiments, it is preferred that the modifying agent isfast-acting, i.e., it reacts in less than one minute, and often, in lessthan 30 seconds. Various additives that may increase the reaction timeof the modifying agent include silicon, styrene and alpha-methylstyrene,and bis-cyanoacrylate, and particles such as clay, nanoclays,montmorillite clay, and carbon black. NaOH, either as a 50% solution inwater or as pellets could also be added to increase the reaction rate,e.g., for cyanates. Gases, e.g., ammonia, may increase reactivity.Additives could be added to increase the pressure within the modifyingagent, thus forcing it out of the repair conduit quicker; these includetriacetone triperoxide and butane. Some of these same additives mayimprove water resistance of the reacted product. Bis-cyanoacrylate mayalso increase the strength of the reacted product.

The additive may be added directly into the modifying agent(s), or, beprovided in conduits or other sources proximate the modifying agent.Alternately, the conduit could have the additive or the modifyingagent(s) on its surface.

According to the present disclosure, it is proposed to coat fibers witha modifying agent or other second modifying agent which can have a ROMPreaction and react more than once, or go on reacting past where ittouches first. It is believed that coating conduits such as fibers withcertain modifying agents can have a beneficial effect and produce afast, efficient reaction but also could be used to create a pre-preg orcomposite material in one step with no mixing. Rather than beingprovided on the outside, the modifying agent could alternately beencapsulated, and only a small amount needs to be released to start thereaction with the modifying agent and formation of the resin. Thecomponents can later be activated for self-repair.

10. Various Features

The following lists provide various features such as ingredients formatrices, conduits, modifying agents, additives, etc. that can be usedin any or all of the applications described in this disclosure. Alsoprovided are different properties and characteristic of variousfeatures.

The damage forces that the systems of this disclosure can repairinclude: impact fatigue; cycling; thermal cycling creep. Also forcesform processing such as inherent stresses can be damages which can beutilized later for repair.

The force of damage may be moderate, e.g., from 5 to 50 joules, may behigh force (e.g., for graphite with tubes) to ballistic forces (e.g. ifrepair chemical in the matrix as a metal particle and uses heat ormelting to flow). The velocity of the damage may occur at the speed ofgravity to bullet speed. The damage itself may be delamination,cracking, fiber breakage, or buckling. The damage may be caused by oneor multiple damaging events. The damage may be instantaneous or occurover several years, e.g., for fatigue, thermal cycling and creep whichhappens repeatedly over time.

The flow of the repair modifying agent out from the conduit could occurwithin a nanosecond (e.g., for a very thin material, e.g., 100-1000centipoise) to several days.

The speed of complete chemical reaction, for the modifying agent, may beless than a week, less than a day, a few hours, less than a minute, oreven less than 30 seconds. In some embodiments the speed of repair maybe less than 1 second.

In general, for fiberglass laminates, the heat of processing is fromambient to 250° F., usually for at least one hour; for graphitelaminates, the heat of processing is from ambient to 300-350° F.,usually for at lest two hours. Either or both may be at pressure of 0psi (total vacuum) to 10,000 psi. The preferred manufacturing of selfrepairing laminates may include vartm, scrimp, the use of an autoclave,manual or hand lay up, resin transfer molding, resin injection, etc.

For self-repair composite, the matrix may include polymer, pre-preglaminates, laminates, metal, metal-polymer, ceramic, glass, and evenwood. The polymers can be thermosetting or thermoplastic materials.Polyetheretherketone (PEEK) and poly phenylene-ether (PPE) relatedpolymer are examples. The composites could be processed at temperaturesover 200° F., and as high as 300° F. Thermosetting materials can beprocessed at 250° F. for one hour and alternately or additionally at300/350° F. for 2 hours. Some thermoset laminates are processed at 250°F. for one hour and alternately or additionally at 300/350° F. for 2hours. Some thermoset laminates and polymers can be processed at 30-700°F. Usually, thermoplastics are processed up to 200° F., and can beprocessed at pressures of 40 to 10,00 psi.

Other matrices could be metals or aluminum foam with polymer infill thatself repairs.

Numerous examples of repair chemicals or modifying agents have beenprovided above. Of course, these include epoxies, cyanate esters,cyanoacrylates and could include DCPD, Grubb's ruthenium, iron, tin,osmium, etc. These modifying agent need to survive the heat and pressureof processing, and in some designs, can remain reactive at minus 65 F,can repair damages from 2 to 60 joules of energy, can repairdelamination of 1.times.1 to 21/2 by 21/2 inches by many layers deep,can move in 1 to 30 seconds and chemically react fast in less than 30seconds.

Examples of useable epoxy resins include: e-05 CL Hysol; 608 Hysol;Hysol EA 9396 QT system; Resin lab EP1121 clear (Part B); Resin lab EP750 clear (Part A); Ultra interior latex semi-gloss enamel; Epon Resin828; Epoxy and fiber glass thinner; Bisphenol F-Epoxy resin (EPALLOY8230); Resorcinol Diglycidyl ether (ERISYS RDGE); Epoxy phenol novalacresin (ERISYS RN-3650); Bisphenol F-epoxy resin (ERISYS RN-25);Epoxidized phenol-Novolac resin (ERISYS RF-50); Epon resin 8161; Eponresin 8021; Epon resin 8111; Fireban Hardener (NFC 2836); Fireban Resin;NFE-3038; NFE-2835; NFA-4822; NFA-3444; Fireban hardener (NFA 3140);Phenolic Novolac resin; and Epoxy novolac resin. For most, thedifference between these epoxies and the commonly known epoxies is thatthese are formulated with Bis F or novolac epoxy resins (as compared to‘ordinary’ Bis an epoxy resins). They provide an increase in chemicalresistance as compared to the normal epoxies.

Examples of useable cyanate resin ester monomers include:2,2-bis(4-cyanatophenyl)propane (Badcy); Aquafill 5003; Aquacore 1024;Aquapour 4015; Aquapour 1024; Aqua seal 3036; Aqua seal 3818; Aquacorepremium 6001; Resbond 944; Luperox DHD-9; Resbond 940; and epoxy vinylester resin. These are highly innovative high-temperature, water-solublemandrel materials.

Additional examples are: MY0150 resin; Trithanolamine; Resin beads;Urethane pour foam (PART A); Urethane pour foam (PART B); McLube 1725;Resbond 940 (Fast cure adhesive); and D.E.R 354 liquid epoxy resin.

Examples of suitable solvents, for missing of epoxies and otheradhesives, include: acetone extra strength; glycerol 99% for high tempproduction; and Duratec Black recoating.

Example of aromatic amines that could be used include: Aradur 976-1aromatic amine; and Two part Amine compound. Methylmethacyrlates, couldbe used, as could methacylic acid.

Some useable polymer chains cleave leaving hydrogen of polyphenylene-ether (PPE) related polymer composites, re-bonding reactionproceeded at the chain ends with copper/amine complex added as acatalyst. Redox reaction for supplying oxygen continuously in theoxidation state of copper is changed from a mono-valent state to adi-valent state that was active for the re-combination reaction betweenchain ends in polymer.

Other chemicals for polymers self repair chemical include bistriazine,which reacts with tripehenol phosphenes in 15 minutes at roomtemperature, and cross-links at higher temperatures; resourcenoldiglyceride ether mixes.

High temperature resistant materials, such as boron fibers, aresuitable. B.sub.4C (boron carbide) in carbon composite, when it melts,oxidizes to B.sub.2O.sub.3 having a higher melting temperature. SiCwhich oxidizes into SiO.sub.2 may also be suitable.

Various additives may be added for matrix strength. These have a goodpolar functionality hence can trap hydroxyls on their surfaces:Nanoclay, and carbon lampblack.

Heat producing chemicals may be added for heat production, potassiumpermanaganate, and a mixture of glycerin and potassium permanganate.Electrical wire may be physically inserted, such as for deicers onhelicopters. Additives may be used that repair based on heat generatedby the product—e.g., tires, computers.

The repair conduits, also sometimes referred to as tubes or fibers,could be fiberglass, cement, asphalt, hydroxyapatite, glass, ceramic,metal, polyolefin, polyester, polycarbonate, polyacrylate, polyarylate,polyamide, polyimide, polyaramide, polyurethane, carbon, graphite,cellulose, nitrocellulose, hydrocarbon, or piezoelectric material. Otherexamples include silicon glass tubes of 600 to 1200 micrometer outerdiameter, borosilicate glass tubes, optical fibers from PolymicroTechnologies, having an outer diameter of 60 to 1200 micrometers,silicon with polyimide or other polymer coatings, polyethylene tubes.Various processes could be done to treat the tubes.

The conduits or tubes could be nanofibers, electrospun nanotubularfibers, nanotubes, or hollow nanowhiskers. The nanofibers and like aresufficiently small enough so that no (or minimal) bumps are raisedbetween pre-preg plies. Some fibers could be as small as 20-120micrometers.

Some of the following features can be used for treating tubes (e.g.,borosilicate) in order to reduce the curing rate of the modifying agentmaterial therein, (e.g., cyanoacrylate): distilled white vinegar (e.g.,overnight), muriatic acid, DL-maliec acid, dichloro, and dimethylsilane. These materials can be used for coating the glass tubes in orderto make them hydrophobic and/or slippery. The tubes could be etched tomake them more susceptible to breakage on impact.

The tubes, channels, fibers, or the like may be present as a weave ofinterconnected conduits. This weave could be designed to first carry thestructure forming resins, resin infusion or scrimp, and then in the samechannels carry self-repairing chemicals. The conduits could be used forsecondary purposes, such as to carry light, energy or electricity.

Dyes or color changing indicators could be added to the matrix,modifying agent, or any additives. These include food colors,bromocresol purple, bromocresol green, bromothymol blue, sulforhodamineB, and cyanoacrylate that can indicate that it has reacted by a colorchange. Some cyanoacrylate changes color when reacted.

Any part of the composite may be configured to sense changes of one typeor another. The composite may include nanotubes, carbon black, metalparticles, reinforcements such as fibers, clay, carbon black, beads. Thesensing may be based on visual change, energy release, eddy currents,energy differential, or the like.

Functionally gradient materials can be added anywhere within thecomposite. Functionally gradient materials can be thought of asspatially varied but produced by changes over time. To create gradientmaterials by changes during processing, they can be formed with fibersdifferent from the pre-preg, by adding the variant fibers in between twonon-zero bleed pre-preg layers to make an in-situ pre-preg layer. Thebleeding of the resin during processing will form a prepare layerincorporating these fibers. Another way of making an in-situ laminatelayer, in this case using different resin systems, is to lay in resinrods or a plaque which melt during processing and can fill in around dryfibers. These two in-situ ways of making pre-pregs with various resinsand fiber contents will not disturb the manufacturing process and willallow the incorporation of various composite functionally gradedproperties.

The incorporation of the variant fibers needs a source of extra resin,either from the extra resin from other layers or additional resin fromtubes or plaques. The variant resin needs fibers to attach to, eitherfrom the adjacent pre-preg layers or fibers. The combined system wouldconsist of variant fibers or fiber performs set in a layer with avariant set of resin tubes or a plaque.

The particular application for development is for improved gradientthermal protection, oxidation protection, and impact strength propertysystems. For some embodiments, e.g., self-forming systems, the followingmaterials could be used: gydroxyapatite chemicals, (which are polymersthat react with water forming hydroxyapatite bone structures or cementpolymer composites), hydroxyapatite nanocrystals, and B-TCPhydroxyappetite nanocrystals. For ceramic/polymer self-formingstructures, nylon polymer could be made with maleic acid andhexamethylene diamine. Succinic acid could also be used.

Uses force from processing inherent stresses for later release such aselectrostatic charge in paint.

The systems of this disclosure provide various advantages for concretesystems. The adhesive is flexible itself and keeps on releasing witheach brittle failure, i.e., crack. The ability to fill in fordimensional gaps with chemicals that foam, even with internally releasedstiff non-foaming adhesives, such as cyanoacrylates. The self-repairsystem can replace the tensile strength given by steel rebar. In fullscale bridge applications, surface drying cracks can be avoided bycreating in-situ control joints. The system can transform an entirestructure into a ductile material, with energy dissipated all over ascracks form, and consequently, catastrophic failure, due to theenlargement of any one crack, would be prevented. The system helpsprestressed members by re-bonding the tendons to the concrete, shouldany become debonded.

11. Examples

The following illustrative examples show that the modifying agent(s)survived high temperature processing (e.g., 250° F. processing forfiberglass and 300-350° F. processing for graphite laminates) and werestill reactive after the exposure.

Two different modifying agents were used, epoxy and DERAKANE epoxy vinylester. The matrix used was a graphite epoxy made by Hexcel.

Thirty-two (32) plies of unidirectional carbon pre-preg were used andextra plies were added to level out the samples, i.e., to reduce anywaviness caused by the addition of the repair tubes. The carbon pre-pregwas cut to remove material to allow for tube placement in the center ofthe stack of pre-preg plies.

The 32 layers were stacked in a quasi-isotropic manner. After half(i.e., 16) of the layers were positioned, several filled conduit tubeswere placed on top. For two-part adhesives, such as epoxy, twinnedconduit tubes were placed next to each other. For a unidirectionallaminate, the layout of the tubes was at 45 degrees to the pre-pregdirection. Ten (10) pre-preg layers were cut to seat round the tubes,e.g., to level out the top of the tubs with the cut pre-preg layer. Theother 16 plies were placed on top, so that 32 plies of pre-preg (plus 10plies of pre-preg that had been cut) were combined to form the laminate.

The experimental graphite sample laminates, made with 32 plies of carbonpre-preg and 10 extra plies between the tubes, were made usingconventional laminate forming procedures. The stack included a releaseply, a perforated release ply, and bleeder cloth, with a vacuum bag witha central valve. The samples were autoclaved using a vacuum bag attemperature of 250° F. and 350° F. and a pressure of 40 psi with acuring ramp for 34 minutes to 250° F., then a 70 minute soak at 250° F.,then a 22 minute ramp to 350° F. and a soak for 70 minutes and thenfinally cool to ambient temperature. The sample laminates were made aslarge pieces and then cut into smaller individual samples.

The control samples were similar laminates with no repair tubes or withempty tubes. Of course, the experimental samples had the repair tubesfilled with modifying agent.

The samples were tested by impacting with 200 foot pounds of weight. Theimpacts ranges from 9 to 24 inches drop of a 20 pound weight in aGardner impactor.

The samples were then tested in flexure or compression to failure in anInstron machine. The computerized results were normalized and thestandard deviations studied and comparative result made. The differencebetween modulus on flexure of the control-no-tubes and thecontrol-with-tubes provided any penalty for tube insertion into thepre-preg.

The comparison of the experimental samples to the control-no-tubes didnot provide information regarding the overall repair value of the repairtubes. The comparison of the control-with-tubes to the experimentalsamples provided information regarding the strength contribution of themodifying agent. Results are provided below.

TABLE Sample Category Modulus in Flexure (msi) Controls, no tubes, notimpacted 9.535 Controls, no tubes, impacted (est. 4.479 from other data)DERAKANE, flexed 1 day after impact 4.86 DERAKANE, flexed 5 days afterimpact 5.78 DERAKANE, flexed 9 days after impact 8.425 Epoxy, flexed 5days after impact 7.2 Epoxy, flexed 9 days after impact 7.19

In fiberglass samples, a visual inspection with light penetratingthrough the samples was done using a dyed modifying agent for easieridentification of the damaged area. In graphite samples, the laminatewas pulled apart to assess the size of the delamination and the spreadof the modifying agent.

The samples that used epoxy as the modifying agent, the results wereacceptable. In examples using DERAKANE as the modifying agent, thesesamples did not withstand the high temperatures of processing.

In subsequent tests, the DERAKANE was added to the tubes after the heatprocessing of the laminate; i.e., the DERAKANE was added to open endedtubes. The samples were processed as above but the open ended tubes wereplugged during the heating process so as to not take in resin flowingduring the processing. After heating, the tube ends were unplugged andfilled with DERAKANE by a syringe pressure set up.

Although the DERAKANE modifying agent was not able to withstand the hightemperatures in this experiment, DERAKANE modifying agent is valuable inthat it can gain strength earlier than the epoxy type reaction, whichrequired time for diffusion, even though the epoxy has a higher ultimatestrength. Additionally, in these examples, the DERAKANE epoxy vinylester provided a higher repair yield than epoxy, about 88% compared to74%, but both of which are acceptable. The epoxy vinyl esters survivedall processing temperatures attempted, although most samples wereprocessed at 300° F.

The following illustrative examples show that doubling the number ofrepair tubes present in the laminate (e.g., in the top and bottomplies), restored damaged areas properties better than single sets.

Samples were made in same way as above except twinned repair tubes witha two-part epoxy (i.e., one part in each tube) were placed two layersfrom the top and two layers from the bottom of the stack of 32 pre-pregsheets. The tubes were placed along the exterior edges of the stack.

With double layers of repair tubes, after impact, the repaired laminatehad a modulus 300% higher than the impacted controls. It was estimatedthat the impacted control was 50% of the non impacted one, the nonimpacted control would be 4.2 msi and repaired samples would have a 40%higher modulus than the undamaged control for a repair value of 140%.

General conclusions reached for graphite laminate composites were:

1. The repair system had no effect on the laminate, i.e. a thick samplewith the embedded glass tubes in the neutral axis behaves the same asone without tubes, in modulus and in flexure.

2. The repair system works, i.e. stiffness is lost after impact and thestiffness is greatly restored as a result of the release of repairagent.

Although several different matrix materials have been disclosed orsuggested herein, others may still be used by those skilled in this art.Although a number of different kinds of fibers have also been described,still other fibers might also be used by those skilled in this art inaccordance with the principles of this invention. Different modifyingagents and different mechanisms for selective release of the modifyingagent in response to an external stimuli or internal stresses caused byother external occurrences might also be developed and designed by thoseskilled in the art given the principles provided herein. Accordingly,all such obvious modifications may be made herein without departing fromthe scope and spirit of the present invention as defined by the appendedclaims.

1. A multifunctional composite comprising: a matrix; conduits disposedin the matrix; and a chemical disposed in the conduits, the compositebeing at least one of able to repair damage due to ballistic force,conductive, radar absorbing, self-repairing when damaged, self-sensingwhen damaged, electricity generating when damaged, and internallypumping when damaged, wherein when the composite is self-repairing orself-sensing, the composite also is at least one of able to repairdamage due to ballistic force, electricity generating when damaged,internally pumping when damaged, conductive, and radar absorbing.
 2. Thecomposite of claim 1, wherein the composite is conductive and furthercomprises at least one of an antioxidant, an anticorrosive, andconductive particles.
 3. The composite of claim 1, wherein the compositeis self-repairing, self-sensing, able to repair damage due to ballisticforce, internally pumping when damaged, and conductive.
 4. The compositeof claim 3, wherein the composite is electricity generating whendamaged, radar absorbing or a combination thereof, and further comprisesat least one of an antioxidant, an anticorrosive, and conductiveparticles.
 5. The composite of claim 1, wherein the composite isself-repairing and able to repair damage due to ballistic force.
 6. Thecomposite of claim 5, wherein the composite is self-sensing.
 7. Thecomposite of claim 5, wherein, when the conduit is damaged, the chemicalfoams or becomes thixotropic.
 8. The composite of claim 5, wherein theconduits are in the form of at least one of springs and channels.
 9. Thecomposite of claim 1, wherein the composite absorbs radar and is atleast one of self-sensing, electricity generating, and conductive. 10.The composite of claim 1, wherein the composite is self-repairing andself-sensing and further comprises metal.
 11. The composite of claim 1,wherein the conduit comprises at least one wall and optionally acoating, the composite further comprising a conductive material, theconductive material being present in at least one of the at least onewall of the conduit, the optional coating on the conduit, the chemicalin the conduit, and the matrix.
 12. The composite of claim 11 furthercomprising additives comprising at least one of nanotubes, metals, andcarbon black.
 13. The composite of claim 11, wherein the composite isself-repairing and self-sensing.
 14. The composite of claim 1, whereinthe conduits are in the form of at least one of springs, porous walledfibers, and channels.
 15. The composite of claim 1, wherein the conduitscomprise an interior wall, the interior wall being coated with an acid.16. The composite of claim 15, wherein the composite is self-repairing.17. The composite of claim 1, wherein the composite exhibits internalpumping when damaged.
 18. The composite of claim 17, wherein thecomposite is self-repairing.
 19. A multifunctional composite comprising:a conductive material; a matrix; a plurality of conduits disposed in thematrix, each conduit defining a volume and comprising at least one walland optionally a coating on the conduit; and a chemical disposed in theconduits, the conductive material being present in at least one of theoptional coating on the conduit, the wall of the conduit, the volumedefined by the conduit, the chemical, and the matrix.
 20. The compositeof claim 19, wherein the composite is self-sensing, the conduits areconductive and in a form of a web, a grid, a weave, a three dimensionalarray, or a combination thereof, and the chemical is reactive with thematrix, and further comprises a dye that changes color when the chemicalreacts with the matrix, and conductive additives selected from the groupconsisting of nanotubes, metals, and carbon black, when the composite isdamaged, the damage is detectable by eddy currents.